Supongo que lo has visto en una canción infantil. "las nubes se levantan" significa que se están formando nubes y por lo tanto hay probabilidad de lluvia. "se levantan nubes" no lo he oído, seria que alguien iza, levanta,alza, sube nubes ??? un poco raro. Si quieres lo puedo intentar traducir al ingles solamente mándame un privado.

I don´t know that phrase or at least i don´t use it but I guess it has to be with the fact that "clouds" don´t let the sky be clear,in a poetic way could mean that "Clouds" are your worries and fears and when they dissappeared you could think more clearly and have a better and positive view about everything.In eglish will be "Sky opens up".On "Las nubes se levantan" it means that clouds are forming and are visible on the sky but "Se levantan nubes" could be both that clouds are forming or they are fading away

I don´t know that phrase or at least i don´t use it but I guess it has to be with the fact that "clouds" don´t let the sky be clear,in a poetic way could mean that "Clouds" are your worries and fears and when they dissappeared you could think more clearly and have a better and positive view about everything.In eglish will be "Sky opens up".On "Las nubes se levantan" it means that clouds are forming and are visible on the sky but "Se levantan nubes" could be both that clouds are forming or they are fading away